The invention relates to a shock or impact detector for carrying on a vehicle, in order to automatically trigger, in the case of a shock or impact, one or more safety systems associated with the vehicle. The invention also relates to an aircraft distress beacon incorporating such a shock or impact detector.
The shock detector according to the invention can be used on all vehicle types, namely land vehicles (cars, buses, trains, etc.), as well as maritime or air vehicles (aircraft, helicopters, etc.).
The nature of the safety system or systems triggered by the shock detector is in particular dependent on the nature of the vehicle carrying it. In the case of land vehicles, they can be systems aiming at protecting from shock or impact persons carried in said vehicle. In the case of maritime and air vehicles, the shock detector usually controls the signal emitter of a distress beacon facilitating the finding and in certain cases identification of the ship or aircraft. When the vehicle is transporting passengers, the shock detector can also control the ignition of emergency light pointers. It can also trigger the putting into operation of an anti-fire safety device.
Although their constructions may differ, the existing shock detectors are all based on the same operating principle. An electric switch, placed in an electric control circuit of the safety system or systems controlled by the detector, is automatically closed by a mobile weight such as a ball, when a shock undergone by the vehicle on which the detector is carried leads to a deceleration of the vehicle exceeding a given threshold. Shock detectors operating according to this principle are more particularly illustrated by U.S. Pat. Nos. 4,873,401 and 4,948,929.
The operating principle of these existing detectors is such that the duration of the shock undergone by the vehicle has no influence on the triggering of the safety systems. However, experience has shown that the consequences of a shock of a relatively small amplitude, but of prolonged duration can be as serious for the vehicle and the persons carried as those induced by a brief, high amplitude shock. Thus, in exemplified manner, the dropping of an aircraft with a very limited incidence onto a wooded area can lead to a prolonged, but limited amplitude shock, which is inadequate to be detected by existing shock detectors, whereas it would justify the triggering of the aircraft safety systems and in particular the emitter of a distress beacon enabling the emergency services to locate and possibly identify in a rapid manner the aircraft.